Electric air-heating system.



E. J. SIVIIIH.

ELECTRIC AIR HEATING SYSTEM.

APPLICATION FILED DEC. 3. 1915.

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ELECTRIC AIR HEATING SYSTEM.

APPLICATION FILED 050.3. 1915.

1,217,229. PaIenIed Feb. 27,1917.

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Patented Feb. 27, T917.

E. I. SMITH.

ELECTRIC AIR HEATING SYSTEM,

APPLICATION man DEC.3.1915.

UNITED STATES PATENT OFFICE.

ELMER J'. SMITH, 0F DETROIT, MICHIGAN, ASSIGNOR TO THE PETER SMITH HEATER COMPANY, 0F DETROIT, MICHIGAN, A CORPORATION 0F MICHIGAN..

ELECTRIC AIR-HEATING SYSTEM.

Specification of Letters Patent. Patented Feb, 2', 1917.

Applicatiomled December 3, 1915. Serial No. 64,811.

To all whom t may concern:

Be it known that I. Emme J. SMrrH, a citizen .of the United States of America, residing at Detroit. in the county of lVayne and State of Michigan. have. invented certain new and useful Improvements in Electric Air-Heating Systems. of which the following is a specification. reference being had thereinto the accompanying drawings.

The invention relates to electric heating systems of that type in which the heat is distributed by convection of air directly heated from the electric units. It is the object of the invention, rst, to obtain a construction which is absolutely safe` being guarded against overheating; second, to obtain an increased `efiicien'cy'and the conservation of all of the heatgenerated; and third, to protect the switch for the heating current from injury. `With these and other objects in view", the invention comprises the construction as hereinafter set forth.

In the drawings:

Figure 1 isa diagram of the system. showing the arrangement of the electric circuits and controlling devices;

Fig. 2 is a sectional plan view of the apparatus;

Fig. 4e is an end elevation;

Fig.` 5 is a sectional plan view with the cover removed.

My improved heating system comprises generally a heating chamber A in which the electric heating units and controlling rheostats are placed` a motor-driven fan B for propelling an air current through said chamber and a distributing conduit C for the heated air. The heating chamber and motor fan preferably constitute an assembled unit, which may be mounted in any convenient location, being particularly adapted for use upon street cars and other moving vehicles.

In specific constructiom the chamber A comprises a metallic casing having heads D and E forming respectively the inlet and outlet conduits for the air. `Within the metallic casing is an insulator lining comprising check-plates F on opposite sides thereof, having metallic contact plates mounted thereon and guides G for positioning and holding the individual units. Each of these -cushion J of yieldable insulating material.

such as an asbestos washer. The two sections are held together by a. metallic rod K extending through a central longitudinal aperture., and having afhook K at one end and a clamping nut K2 at the opposite end. said hook and nut respectively engaging recesses H2 in the ends of the spool to avoid short circuiting. The spool is preferably provided with squared head flanges H3 at its opposite ends and the ends of the. resistor are secured to contacts I passing through said head anges and attached to spring contact plates I2. Thearrangement is such that when one of the units is placed in the heatinglchamber with its opposite ends in engagement with the cheek-plates between the guide strips G the contacts I2 will engage" with the cooperating metallic contacts on the cheek-plates so as to establish the electric circuit through the resistor.

To obtain the requisite heating etiec-t. a

number of the units H are placed in the Fig. 3 is a sectional slde elevation thereof;

chamber A, and as shown there are nine of these units arranged in multiple series of three and three. The contacts on the cheekplates which cooperate with the contacts on the unit are so inter-connected as to formY atively high volt-age system. such as the usual tive hundred volt street railway systems. it is advantageous to use a motor designed for lower voltage and to control the current by a rheost-at. The energy which is consumed by the rheostat may be entirely utilized by placing said rlieostat within the casing A, so that the heating effect produced will be effective in heat-ing the air. As shown, a

plurality ot rheostat coils N are engaged with clip-contacts O' upon an insulator plate l), this being arranged in the forward portion of the casing A or that portion into which the cold air from the fan is iirst introduced. There is also an air switch Q which is adapted to operate by the pressure of air within the casing to control the heating circuit, so that the stopping of the movement ot' air through any cause will result in the ycutting-out of the'heating circuit or a portion thereof to avoid overheating ot the apparatus. et further safeguard is a thermostatic switch which operates at a predetermined temperature and will also effect the automatic cutting-out of the heating circuits. All ot these parts are conveniently arranged within the casing A, so as to be in operative relation.

rlhe electric circuits and controlling devices theret'or are shown in Fig. l. in which R is the service connection from the trolleypole or other source leading to the multiple switch S having. as shown. three separatelyoperable blades S S2 S3. rl`he blade S controls the motor circuit which leads to the motor l` and to solenoids "tl and lil inv series therewith: then through a resistance U2 to a ground U". The solenoids lU and ll control respectively switches V and V' for the heating circuits. and the solenoid U also controls a switch V2 for the motor circuit. All ot' these switches are closed when the solenoids are energized by the closing` of the circuit through the switch blade S. but upon the closing of the switch Y2 a shunt il' for the motor circuit is closed, said shunt containing` a resistor 'W so proportioned to the combined resistance ot the solenoid l?. ot the solenoid U and the shunt resistor V2 that the major portion ot' the motor current will pass through the shunt ll". and only a small portion through the solenoid coils ll and U. rl`he current f through these coils is.l however. sufficient to maintain the switches V V closed. X is a thermostatic switch which is in a shunt X about the resistor U2. aid shunt having a solenoid coil therein. which operates a switch X3 in a shunt X4 about the solenoid U. The arrangement is such that the closing of the thermostatic switch X will ener- ,gize the solenoid X2, closing the switch X3, which will shunt out the solenoid U. thereby opening the switches V and `lla-but the solenoid U still remains in circuit so as to maintain closed the switch V.

rthe switch blades S2 and S3 control separate heating circuits, the former containing a multiple series ot resistor elemen-ts Y Y', and the latter a single series Y2. 'llhere is alsoan additional resistor YS, which forms an auxiliary heating element of high resistance,arranged in abranch circuit Yt in series with the resistors Y Y and Y2 and includ-l ing the switch V. Fll`he main circuit Y5 in series with the resistors Y. Y and Y2, but excluding the resistor YS, including the switch V. connects to ground when switch V is closed. The branch li including the switch V connects with a ground when switch V is closed.

The construction just described is such that the closing of the switch blades S2 and S3 will notI complete the heating circuits, by reason ot the tact that such circuits must include a ground connection through either the branches Y' or the main circuit YS, both of which are initially open: llt is only when the motor circuit closed by the blade S that the solenoids U lU are energized to close the switches "V and Y. This will establish a ground connection tor the heating` circuits, so as to energize the resistor coils Y Y and Y2, but the auxiliary coil it is shunted out by closing oit the lower resistance circuit Y5. ConsequentlyY when all three ot the switch blades S S2 and S3' are closed the resistors Y Y and Y2 will be in operation. and air will be propelled by the motor fan through the casing it to absorb the heat ot said resistors. 't he current tor the heater circuit is necessarily7 ot considerable volume. whereas the current for the motor circuit is comparatively small. l have therefore designed a construction by which the blades S2 and S3 can only be closed or opened when the switch blade S is in open position, in which case the switches V and Y are also open. rllhis prevents any burning of the switch blades S2 and Si. as they can only be operated when their respective circuits are opened by the switchesv Y and V. lVhen., however, either or both of the blades S2 and S2' are first closed and the blade S subsequently closed, the switches V and V. which are electromagnetically operated. will effect a quick closing of the heater circuits. and a corresponding quick opening` is effected by said switches upon the opening of the motor circuit. Any kind of mechanical interlock may be employed tor the purpose just described, but as shown a bar S4 having locking hooks and SG for the blades S2 and Sii is operated by a cam ST actuated by the switch blade S.

As has been described. there is an air switch Q for controlling the motor circuit. which switch is operated by the pressure of air in the chamber As shown, this switch comprises a. movable diaphragm Q attached to a spring contact member Q2, which contacts with a cooperating contact Q3 when there is merely atmospheric air pressure within the chamber-A. The disk Q. is arranged in an opening in the side of the chamber so that a slight rise of pressure ot air in the casing will cause a movement ot said'disk suidicienlt to separate the contacts Q2 and Q3; The switch \is arranged 1n a shunt circuit Z around the solenoids U U and X2. and also around the reslstor U2: or, in other words. a dead shunt forl 5 cutting out Said switch-operating magnets. Thus it will be understood that whenever the switch Q closes through the failure of air current in the casing A, all of the heater circuits will be instantaneouslyv cut-out and will remain cut out until the air current is restablished. f

In the operation of the system, it will be seen that the control of the motor circuit is independent of the control of the heater circuits, so that the air may be propelled through the system whether or not the heaters are in operation. On the other hand, the heater circuits are so dependent upon the motor circuit that none of the heating elements can be energized until the motor circuit is established. and furthermore even under such condition the heaters will not be voperative unlessl air is passing through the chamber A and developing sufficient pressure therein to operate the air switch Q. The degree of heat which is imparted to the air passing through the system may be controlled by properly setting'the blades S2 and S3, but as before stated, these blades must be adjusted while the motor switch is still' open, and therefore do not complete the closing of the heater circuits. lVhen. in the operation of the system, the heat rises within the casing A beyond a predetermined point, the thermostat X will operate, causing the opening of the switch V', which places the auxiliary heating element Y3 in series with the elements Y Y and Y2, therel cutting down on the heat- 40 ing effect. There is, however, a generation of heat sufficient to warm the air, but insuiiicient under any ordinary conditionto raise the temperature to the danger point. Should an abnormal condition occur, as through the failure of the thermostat X to operate or any other part of the automatic mechanism, the apparatus is safeguarded by the thermal cut-outs L, these being arranged within the chamber At` where they are subjected to the heat of the resistor units and will be fused by an abnormally high temperature. and will thereby cut-out the heating circuits.

IVhat I claim as my invention ist---` l. In an electric heating system, the com-' bination with a heating circuit, of a circuit of higher resistance, manually-operable switches for respectively controlling said circuits, a second switch for the heating circuit automatically operated by the closing of the high-resistance circuit, and means for preventing operation of the manually-operable switch for the heating circuit when the high-resistance circuit is closed.

2. In an electric air heating system, the

motor circuit automatically closed upon the combination with a heating circuit, of a motorl circuit of higher resistance, manually-operable switches for controlling the re-l spective circuits, a second switch for, controlling the heating circuit, automatically closed by the closing of saidhigh-resistance circuit, and means for preventing the operation of said manually-operable switch for the heating circuit when said motor circuit switch is closed. 3. In an electric heating system, the combination with an electric motor-propelled fan and an air conduit connected therewith, of an electric heating unit in said conduit, a circuit for said unit, an electric circuit for said lnotor of higher resistance than said heating circuit, manually-operable switches for respectively controlling said heating and motor circuits, a second switch for said closing of said motor circuit, and means operable on the closing of said motor circuit for locking the manually-operable switch of the heater circuit from operation.

4. In-an electric air heating system, the combination with an electric air heater and amotor-driven fan for propelling air to said heater, of electric circuits for Saidheater and motor, and manually-operable switches for respectively controlling said heater and motor circuits, an electromagnetic operating device in said motor circuit for automatically closing a second switch in said heater circuit, a shunt about said electromagnetic device, and a thermostatic switch for closing said shunt.

5. In an electric air heating system, the

'combination with an electric heating unit 'for 'heatmg the air and a motor-driven fan for propelling air to saidheatr, of electric circuits for said heating unit and fan, manually-operable switches for respectively controlling said heating and motor circuits, a second switch for controlling said heating circuit automatically closed upon the closing of said motor circuit, thermostatic means for opening said second switch, and a high-resistance circu-it for said heater operable when said second switch is opened by said thermostat.

6. In an electric air heating system, the combination with an electric heating unit and a motor for propelling air to said heater, of electric circuits for said heater and motor, manually-operable switches for respectively closing said heater and motor "circuits, a second switch for said heater circuit automatically operated by the closing of saidv motor circuit, a high-resistance branch of said heater circuit uncontrolled by said second switch, a switch for closing said high-resistance branch, automaticallyoperated on the closing of said .motor circuit, and thermostatic means for opening said second switch` 130 '4'. lin an electric air heating system, the combination with an electric heater and an electric motor for propelling air to said heater, of electric circuits for said heater and motor, manually-operable switches for closing saidheater and motor circuits, a second switchvfor said heater circuit, electro-magnetic means in said motor circuit for closing said second switch, an auxiliary heaterin series with` said iirstfmentioned heater in a branch of said heater circuit independent of said second switch, a switch in said auxiliary heater branch, electro-magnetic means in said motor circuit for closing said last-mentioned switch, a switch coacting with said second switch for shunting a portion of the current of said motor circuit from said electro-magnetic operating devices, and al thermostatic switch for further shunting the current from the operating device of said second switch to permit the opening thereof while said motor circuit is closed.

8. In an electric air heating' system, the combination with motor-driven means for propelling air and an electric heater for said air, oi'l electric circuits for said motor and heater, means dependent upon the closing of said motor circuit for the closing of said heater circuit, and thermostatic means con trolled b y the heat of the air for increasing the resistance of said heater circuit to diminish the heat generation thereof.

9. ln an electric air heating system',V the combination with motor driven means for propelling air and an electric heating unit for heating1 the air, of circuits for said motor and heater, switches for closing said heating and motor circuits, electro-magnetic means in said motor circuit for closing a normally open switch in the heater circuit, a shunt about said electronagnetic means, and means operated by the pressure of air propelled by said motor for opening said shunt and to thereby effect the closing of the heater circuit.

10. ln an electric air heating system, a combined air propelling and heating unit, comprising a casing having a heating chamber, a fan motor mounted thereon and delivering air into said heating chamber, a distributing conduit connected to said heating chamber, electric heating units in said casing in the path of said air, and a motor rheostat also in said heating chamber, the coils thereof forming supplemental heating units.

11. lln an electric air-heating system, a casing, a heating unit Within saidcasing comprising a resistor, an insulating body and contacts carried by said body, a pair of insulating members the extremities of said unit, contacts respectively carried by the insulating members for engagement With those carried by the unit,

respectively engaging i propelling air,

said insulating members being vrespectively formed with portions engaging the extremities of the unit andI acting to maintain the contacts of the unit engaged with those of the insulating members.

12. In an electric air heating system, a casing, parallelly-arranged insulator cheekplates on opposite sides of said casing having parallel guides formed thereon, terminal contacts mounted on said cheek-plates` a plurality of detachable heating units having end contacts and adapted to engage the guides of said cheek-plates to be moved into engagement with the coperating contacts on said cheek-plates, an insulator cover plate, a thermal cut-out mounted on said cover plate, and contacts Connected therewith for engaging contacts on said cheekplates to complete the circuit through a series of heating units.

13. 1n an electric air-heating system, the combination with a casing, of a pair of insulator cheek-plates disposed therein, each having a groove, said Igrooves being in opposite relation, a plurality of detachable heating units having end contacts and adapted to be successively engaged in said grooves, each unit determining the position ot' the succeeding unit in eachv groove, and a plurality of contacts mounted upon each cheek-plate, in a. spaced relation such as to be respectively engaged by the end Contacts of the units.

14. In an electric air-heating system, a casing, insulator cheek-platestherein having 10Q grooves upon their opposing faces, a plurality of heating units having end contacts, the ends o1" said units being engageable in said grooves, and contacts upon the cheekplates, said grooves functioning to guide the 10.: units into positions of engagement between their end contacts and the contacts upon the cheek-plates and'further functioning to maintain such engagement.

15. ln an electric air heating system, a 110 casing,

a motor fan mounted at one end thereof and discharging air thereinto, a distributing air conduit connected to the opposite end of said casing, parallelly-arranged insulator cheek-plates upon opposite sides of said casing having grooved guides therein,

a plurality of heating units detachably engaging said guides and insertible into predetermined positions Within said casing, each unit comprising an insulator spool for extending between the cheek-plates a- Aresistor mounted on said spool and contacts at the spool ends, and inter-connected cooperating contacts upon said cheek-plates for completing the heating circuit through a series of said units.

16. In an electric air-heating system, the ycombination With motor-driven means for and an electric heating unit for heating the air, of circuits'for said mo- 130 tor and heater, switches for closing said circuits, a normally-open switch in the heater circuit, electro-magnetic means in the imotor circuit for closing said switch, a shunt about said electro-magnetic means, and means for opening and closing said shunt according as the motor is started or stopped.

17. In an electric air-heatin system, the combination with a heating circuit having normally-closed high and low resistance branches, of a thermostatic means for opening the low resistance branch under abnormal temperature conditions. V

18. In an electric air-heating system, the combination with a heating circuit, of a circuit of higher resistance, manually operable switches' for respectively controlling said circuits, a second switch in the heating circuit, an electro-magnetic operating device in the higher resistance circuit for automatically closing said second switch, a shunt about said electro-magnetic device, and a thermostatic switch for closing said shunt.

19. In an electric air-heating system, the combination with a heating circuit, of a circuit of higher resistance, manually operable switches for respectively controlling` said circuits, a second switch for the heating circuit, automatically operated by the "closing of said high-resistance circuit, thermostatic means for opening said second switch, and a high-resistance circuit for said heating circuit operable when said second switch is opened by said thermostat.

20. In an electric air-heating system, the combination with a heating circuit, of a circuit of higher resistance, manually-operable switches `for respectively controlling said circuits, a second switch for the heating circuit, automatically operated by closing of said higher resistance circuit, a high-resistance branch of said heating circuit uncontrolled by said second switch, a switch for closing said high-resistance branch automatically operated on the yclosing of said higher resistance circuit and thermostatic means for opening said second switch.

21. In an electric air-heating system, the combination with a. heating circuit, of a circuit of higher resistance, manually operable switches for respectively controlling said circuits, ay second switch for the heating cir cuit, electro-magnetic means in said higherresistance circuit for closing said second switch, a switch coacting with said second switch Vfor shunting a portion of the current of said higher-resistance circuit from said electro-magnetic operating device, and means for preventing operation of the manually operated switch for the heating circuit when the higher resistance circuit is closed.

29.. In an electric air-heating system, a casing, insulator cheelcplates oppositely disposed within said casing, a heater unit adapted to bridge between said cheek plates, contacts oppositely carried by the cheek plates and resilient contacts carried by the end faces of said heater unit and engage-able with the contacts of the cheek plates, said heater unit being proportioned in length to subject the contacts carried thereby to a. stress acting longitudinally of said unit when the same is inserted between the cheek plates.

Q3. In an electric air heating system, the combination with two spaced insulating members each having a groove., said grooves being opposed, of a plurality of heater units successively engageable with said grooves, a series of contacts in said grooves and contacts respectively carried by the ends of theheater units engageable with those in the grooves.

In testimony whereof I aiiix my signature in presence of two witnesses.

ELMER J. SMITH.

lVitnesseS:

C. REMELIUS, M. J. PHELAN. 

